Here's Nationmaster's figures. I believe their source is the UN.
Here's what the U.S. Census Bureau says. Their only guarantee of accuracy is our own population, though.
This one's got counters. Whee!
lol
If there is a counter, will Japan be counting down?
Population *density* is important, too.
India has not only the 2nd largest population but also very high (#30?) density.
China, not so much. US, not so much.